Insecticides, acaricides and nematicides are widely used to prevent or at least decrease damage of unwanted organisms to crops. These chemicals can be applied on the soil before sowing, and/or before and/or after the seedlings have emerged. Insecticides, acaricides and nematicides can also be added to the seed as a seed treatment. A seed treatment including an insecticidal, nematicidal or acaricidal active ingredient can include one of these types of compounds only, but can also include a mixture of two or more of the same type of compounds. In addition, the insecticidal, nematicidal and acaricidal active ingredient, or the mixtures thereof, could be used in a mixture with at least one other insecticide, acaricide or nematicide. One or more fungicidal compounds could be mixed with the above mentioned (mixtures of) insecticides, acaricides or nematicides as well. In this document, references to insecticidal seed treatments also relate to seed treatments including a nematicidal or acaricidal active ingredients, as well as to seed treatments including the said mixtures of compounds.
The use of seed treatments is a growing market (Halmer, P. 2004. Methods to improve seed performance in the field. In: Handbook of seed physiology. Applications to agriculture. Eds: Benech-Arnold, R. L. and Sánchez, R. A.), because the use of seed treatments has several advantages over the use of spray or granule applications (e.g. Altmann, R. 2003. Pflanzenschutz-Nachrichten Bayer 56(1), pp 102-110; Hewett, P. D. and Griffiths, D. C. 1986. Biology of seed treatment. In: Seed treatment. Ed: Jeffs, K. A.). Seed treatments protect the seed from sowing onwards. Good overall protection in the early growth phase results in healthy and vigorous plants that better tolerate stress situations. In addition, the total amount of product needed is lower than with spray or granule applications. Crop protection by means of seed treatments also includes many advantages for farmers. The need for other insecticide applications is smaller and the farmers do not need to calculate and prepare tank mixings. Both aspects result in time saving. The moment of spraying crop protection chemicals is very weather dependent, but this problem is not an issue for treated seeds.
Agrochemical companies develop formulations especially suitable for the application as a seed treatment. Such formulations can be added to the seed in the form of a film coating. Characteristically, a film coating is a uniform, dust-free, water permeable film, evenly covering the surface of all individual seeds (Halmer, P. 2000. Commercial seed treatment technology. In: Seed technology and its biological basis. Eds: Black, M. and Bewley, J. D.). Besides the formulation, the coating mixture generally also contains other ingredients such as water, glue (typically a polymer), filler materials, pigments and certain additives to improve particular properties of the coating. Several coatings can be combined on a single seed. In this document, ‘seed treatment’ refers to the application of a film coating on seeds including a formulation with at least one insecticidal, acaricidal or nematicidal active ingredient, including also the possibility of using the coating in or on a pellet, as well as including the insecticidal, nematicidal or acaricidal seed treatment formulation directly into the pellet mixture.
Seed pelleting is a technique that is primarily intended to change the natural shape and size of the raw seed, and the technique can be combined with film coating (Halmer, P. 2000. Commercial seed treatment technology. In: Seed technology and its biological basis. Eds: Black, M. and Bewley, J. D.). Pelleting creates round or rounded shapes, which are easily sown with modern sowing machines. A pelleting mixture contains at least glue and filler material. The latter could be, for example, clay, mica, chalk or cellulose. In addition, certain additives can be included to improve particular properties of the pellet. A seed treatment formulation comprising at least one insecticidal, acaricidal or nematicidal compound can be added directly into the pelleting mixture. In addition, several combinations with film coating are possible: the film coating can be added on the outside of the pellet, in between two layers of pelleting material, and directly on the seed before the pelleting material is added. Also more than 1 film coating layer can be incorporated in a single pellet. A special type of pelleting is encrusting. This technique uses less filler material, and the result is a ‘mini-pellet’.
A variety of techniques and machines exist to apply film coatings, and many of these can also be used or adapted for seed pelleting. Manufacturers of seed treatment machines are, for example, Gustafson Equipment, Satec and SUET. Techniques and machines vary in the method of applying the seed treatment mixture to the seed and the blending process (Jeffs, K. A. and Tuppen, R. J. 1986. Applications of pesticides to seeds. Part 1: Requirements for efficient treatment of seeds. In: Seed treatment. Ed: Jeffs, K. A.). The mixture, for example, can be added by means of a spinning disc atomizer or spreading brushes. The seeds and the mixture can be blended by means of an auger, in a drum, or in rotating troughs. If the amount of film coating mixture added is low, and can be absorbed by the seed itself with only a slight (typically less than 1%) increase in seed moisture content, no additional drying step is necessary. This principle is called self-drying (Black et al., 2006. The encyclopedia of seeds. Science, technology and uses). Otherwise, a drying powder (such as talc) could be added, or an additional drying step is necessary. This step could be integrated in the equipment for film coating, such as in the SUET rotary seed treater with integrated fluid bed dryers. Some SATEC batch coaters are equipped to be connected with drying air also.
A disadvantage of the use of crop protection chemicals is the fact that they can negatively affect crop plants themselves, and this also holds for seeds when the chemicals are added as a seed treatment (Halmer, P. 2000. Commercial seed treatment technology. In: Seed technology and its biological basis. Eds: Black, M. and Bewley, J. D.; Halmer, P. 2004. Methods to improve seed performance in the field. In: Handbook of seed physiology. Applications to agriculture. Eds: Benech-Arnold, R. L. and Sanchez, R. A.). Seed safety is thus affected. The seed treatment including at least one insecticidal, acaricidal or nematicidal active ingredient might result in a slower and less uniform germination of the treated seeds. Basically, germination is defined as the moment at which the radicle protrudes the seed coat or the pericarp. In case seeds are sown in substrate fully covering the seeds, germination is defined as the moment at which the seedlings emerge from the substrate (i.e. emergence). Than, a slower germination results in a slower emergence of the seedlings. Throughout the text, the definition of germination of seed stated above is followed, and used interchangeably with the emergence of seedlings, unless stated otherwise. The seed treatment could also influence the maximum germination and the vitality of the seedlings. Vital seedlings are healthy seedlings that can develop in normal yield-producing plants. The seed treatment could result in a lower vitality and even in a higher number of abnormal seedlings or dead seeds. Negative effects of the seed treatment on germination and vitality can be assessed in experiments under controlled conditions in the climate chamber, greenhouse or germination cabinet in the laboratory, as well as in the field.
If negative effects of seed treatments on seed safety occur, these are generally accepted because the benefits of the seed treatment outweigh the costs, but after all they are disadvantageous in modern farming systems. A delay in germination increases the risk (and duration) of the seeds being attacked by disease-causing organisms or soil pests (Jonitz, A and Leist, N. 2003. Pflanzenschutz-Nachrichten Bayer, 56(1), pp 173-207). A slower and less uniform germination could also affect subsequent spraying treatments. Many herbicides, for example, are most effective at a specific developmental stage of the seedlings. Principally, delayed germination also shortens the growing period of the crop which might lead to reduced yields. Finally, if the vitality of the seedlings is affected, this could result in a decrease of number of marketable plants, which could result in yield loss as well.
The invention includes a method to improve the germination of seeds and the vitality of seedlings of agricultural, vegetable or flower seeds treated with a seed treatment including at least one insecticidal, acaricidal or nematicidal active ingredient.